The invention relates to an electromechanically actuable motor vehicle brake having an actuator subassembly, including a housing, a servo element which is movable in relation to the housing, for moving a brake pad, a motorised drive, a movement mechanism arranged between the motorised drive and the movable servo element, and a gear arrangement associated with the movement mechanism, wherein the movement mechanism has a ball screw with a spindle that can be driven in rotation and a nut that can be displaced linearly in the housing, wherein the nut may be moved, for moving the brake pad, by driving the spindle in rotation within the housing.
Electromechanically actuable motor vehicle brakes of this kind are known from the prior art.
For example, WO 2008/037738 A1, and corresponding US Patent Publication No. 2009/0283371 A1, both of which are incorporated by reference herein in entirety, describes a motor vehicle brake which is actuable both hydraulically and electromechanically. In a normal service situation, that is to say when the motor vehicle is travelling, this motor vehicle brake is conventionally actuated hydraulically. To activate a parking brake, however, the electromechanical actuation function is activated. For this, an electric motor is triggered, which drives a spindle-and-nut arrangement by way of a movement mechanism with a gear arrangement. The gear arrangement is constructed with a worm gear transmission such that it is self-locking, in order to prevent the parking brake action being reduced while the parking brake is activated. However, the self-locking has the disadvantage that within the scope of its electromechanical actuation this motor vehicle brake can only be used as a parking brake. The self-locking hinders use of the electro-mechanical actuation function for application during service braking, since it would block release of the brake. Furthermore, this device provides a mechanical energy storage device which is pre-tensioned by way of the electric motor when the spindle-and-nut arrangement is actuated. The particular feature of the motor vehicle brake described in this prior art lies in the construction of the spindle-and-nut arrangement, in which the rolling bodies do not revolve but are pre-tensioned by way of a spring.
WO 2009/046899 A1, and corresponding U.S. Pat. No. 8,051,957 B2, both of which are incorporated by reference herein in entirety, also describes a motor vehicle brake which is actuable electromechanically. However, the electromechanical actuation is performed both for activation of the service braking function and for activation of the parking brake function. For this reason, the gear arrangement is constructed not to be self-locking. This motor vehicle brake has the advantage that there is no need for a complex hydraulic system for triggering it, but instead the onboard electronics of the vehicle can be used to trigger the braking system. Since the gear arrangement itself is constructed not to be self-locking, for the parking brake function a separate blocking means is provided for blocking the motor vehicle brake, by means of which a lever can be brought into a blocking position magnetically. This prior art also provides for a store of clamping force to be provided, for compensating for settling on the brake pads as a result of cooling or similar once the brake has been applied on operation of the parking brake.
Furthermore, a similar arrangement is disclosed in DE 10 2007 046 952 A1.